Well, I tried to run Automation after two months.
After workshop update stuff I ran it, and in time of loading, those errors happened (in order; second one appeared when I clicked OK).
I haven’t tested the game without my actual cars/engines/companies/other files, but seems like that it would fine.
If it happens with older cars those probably at some point got corrupted by a broken version of the game or are so old that we don’t support them anymore. There is nothing we can do about that.